U.S. patent number 4,701,852 [Application Number 06/638,841] was granted by the patent office on 1987-10-20 for method and device for signaling that gear change is required.
This patent grant is currently assigned to AB Volvo. Invention is credited to Stefan Ulveland.
United States Patent |
4,701,852 |
Ulveland |
October 20, 1987 |
Method and device for signaling that gear change is required
Abstract
Method and device for signaling to a vehicle operator that a
higher gear should be selected. A microprocessor is connected so
that it can sense the rotational speed of the engine and the
vehicle road speed. The quotient of the road speed and the engine
speed is determined and is compared with a series of predetermined
quotients, one for each of the gear selector positions, and the
engaged gear is thus determined. For each gear there is registered
the quotient of its own gear ratio and that of the next higher gear
position, the quotient being zero for the highest gear. The engine
speed signal is multiplied by this gear ratio value for the gear
engaged and is compared with a maximum value, and if the result
exceeds the maximum value, a signal is sent to indicate that a gear
change should be made. In accordance with a preferred embodiment,
the fact is utilized that the generator, if the generator belt
slips, will produce an engine speed value which is too low, so that
the first mentioned measured quotient will not agree with the
predetermined quotient. An error indication is then sent indicating
the need for service.
Inventors: |
Ulveland; Stefan (Gothenburg,
SE) |
Assignee: |
AB Volvo (Gothenburg,
SE)
|
Family
ID: |
20348884 |
Appl.
No.: |
06/638,841 |
Filed: |
August 2, 1984 |
PCT
Filed: |
December 02, 1983 |
PCT No.: |
PCT/SE83/00425 |
371
Date: |
August 02, 1984 |
102(e)
Date: |
August 02, 1984 |
PCT
Pub. No.: |
WO84/02311 |
PCT
Pub. Date: |
June 21, 1984 |
Foreign Application Priority Data
Current U.S.
Class: |
701/64; 340/439;
340/456 |
Current CPC
Class: |
B60R
16/0236 (20130101); Y02T 10/84 (20130101) |
Current International
Class: |
B60R
16/02 (20060101); B60K 020/08 (); B60K 041/06 ();
G06F 015/20 () |
Field of
Search: |
;364/424.1 ;340/52F
;74/866 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
7881 |
|
Feb 1980 |
|
EP |
|
2926070 |
|
Jan 1981 |
|
DE |
|
3128080 |
|
Feb 1983 |
|
DE |
|
2084524 |
|
Apr 1982 |
|
GB |
|
2091358 |
|
Jul 1982 |
|
GB |
|
Primary Examiner: Gruber; Felix D.
Attorney, Agent or Firm: Pollock, Vande Sande &
Priddy
Claims
What is claimed is:
1. A device for signaling a motor vehicle operator to change gear
ratios of a gear box connected to an engine of a motor vehicle
comprising:
a tachometer for determining the engine rotational speed;
a computing unit connected to receive a measured speed of said
motor vehicle and said tachometer measured engine rotational speed,
and to determine said selected gear ratio, said computing unit
storing a plurality of factors for each of said gear ratios
representing the ratio of each gear ratio with the next highest
gear ratio and multiplying one of said stored factors corresponding
to said selected gear ratio with said rotational speed to determine
the rotational speed of said engine if the next highest gear ratio
is selected; said computing unit generating a gear ratio change
signal when said determined rotational speed at said next higher
gear ratio exceeds a predetermined minimum, and a signal indicator
for receiving said gear ratio change signal for identifying a gear
ratio change.
2. The device of claim 1, further comprising:
means for detecting the motor vehicle speed connected to said
computing unit; and
said computing unit computing a quotient of said motor vehicle
speed and said engine rotational speed, and comparing said computed
quotient with one stored predetermined quotient from a plurality of
stored predetermined quotients for each of said gear ratios, said
computing unit signaling said operator when said computed quotient
exceeds a respective stored ratio.
3. A device according to claim 2, wherein the engine tachometer
receives signals from a generator driven via a belt by the engine,
and the computing unit determines a deviation between said computed
quotient of said rotational speed and said vehicle speed and the
predetermined quotient corresponding to the selected gear ratio, to
produce an error signal if a deviation is determined.
4. A device according to claim 1, wherein said computing unit
comprises a microcomputer and setting means which can be set to a
learning mode for entering, while driving, the stored quotients of
the engine speed divided by the vehicle road speed for each
selected gear ratio.
5. A device according to claim 1, further comprising a cold engine
sensor for inhibiting said gear ratio change signal.
6. A device according to claim 1, comprising a load sensor for
changing the engine speed which indicates a gear ratio change at
high engine load.
7. A device according to claim 6, wherein the load sensor is an
accelerometer.
8. A device according to claim 6, wherein the load sensor is
disposed to sense the instantaneous fuel consumption of the
engine.
9. A device according to claim 1, further comprising a sensor for
sensing the operating position of the clutch, the neutral position
of the gear box and a released position of the accelerator pedal,
connected to inhibit said gear ratio change signal.
10. A method for signaling a motor vehicle operator to change gear
ratios comprising:
measuring the rotational speed of an engine of said motor vehicle
engine by detecting pulses from a generator which is belt driven by
said motor vehicle engine;
determining which of said gear ratios is selected;
multiplying the measured rotational speed of said engine with a
value representing the ratio of said selected gear ratio and the
next highest gear ratio, whereby a rotational speed of said engine
for said next higher gear ratio is determined;
comparing said next highest gear ratio rotational speed with a
predetermined level; and
signaling said operator to change gears when said next highest gear
ratio rotational speed exceeds said predetermined level.
11. The method of claim 10 wherein said gear ratio is determined by
the steps of:
measuring the road speed of said motor vehicle; and,
determining the quotient of said rotational speed and said vehicle
road speed.
12. The method of claim 11 further comprising:
comparing said quotient with one of a plurality of stored values
which represent a desired quotient for each gear ratio; and
signaling said operator once said quotient is not said desired
quotient, whereby a fault of said vehicle is determined.
Description
The present invention relates to a method of arranging signaling to
a vehicle driver that an upward gear change is required. The engine
speed is measured and compared to a comparative value, and if one
value exceeds the other, a signal is sent to the driver.
The invention also relates to a device for signaling to a vehicle
driver in a motor vehicle which has an engine and a transmission
comprising a manual gear box with a plurality of shift positions
and which includes a tachometer and computing means for signaling
excessive engine speed.
A method and a device of this type are known by German
Offlenlegungsschrift No. 29 26 070 and have come into use in
certain Volkswagen Passat models for example. This known device
works as follows: a lamp (LED) is lit as soon as the engine speed
exceeds a certain value, circa 2000 rpm. The signal means that the
driver should shift up to obtain better fuel economy. If the
highest gear is already engaged, there will be no signal.
The known equipment is intended to solve the problem of preventing
the engine from running at unnecessarily high speed with a view
both to the life of the engine and obtaining good fuel economy. A
few experienced drivers find no difficulty, due to much practice,
in always driving with the highest possible gear engaged for each
occasion, but most other drivers find this to be considerably
difficult. It is true that many cars are equipped with tachometers,
but it is in practice of limited use to many drivers.
A disadvantage of the known solution is that the increments in the
gear box between the different gear speed is not uniform but
decreases in the higher gears. If one changes gears at a constant
rpm in each gear position, the engine speed after the gear change,
which is the relevant rpm in this context, will be different
depending on which gear is selected.
Example: VW Passat
A shifting principle according to which gears are changed when an
engine speed of 2000 rpm is reached gives the following result:
______________________________________ 15 km/h 1st 2000 rpm 2nd
1118 rpm 27 km/h 2nd 2000 rpm 3rd 1333 rpm 41 km/h 3rd 2000 rpm 4th
1407 rpm ______________________________________
An engine speed which is too low will make the vehicle sluggish,
and it is unadvisable to drive at low rpm, especially if the load
is high, since it may even result in damage to the engine in
certain cases. The known solution therefore necessitates making a
compromise between the goal of providing an early indication of
excessively high engine speed and the risk of obtaining too low an
engine speed when shifting up between certain gears.
SUMMARY OF THE INVENTION
One purpose of the present invention is to eliminate this
disadvantage and have the indication take primarily into account
the engine speed which will be obtained if a higher gear is
selected rather than the present engine speed.
These and other purposes are achieved according to the method and
device having the characteristics of the invention.
In accordance with a preferred aspect of the invention, the
combination is also used for measuring both the engine speed and
the vehicle speed and comparing the ratio between them with a
predicted value for the respective gear position. Theoretically,
this ratio should be constant for each gear position. If the engine
speed is measured via the generator, however, the actual engine
speed will not be measured if the belt between the generator and
the engine is slipping. Therefore the ratio between engine speed
and vehicle speed, measured in this manner, will differ from that
dictated by the gear ratio. It is good to be aware of such a
discrepancy, as it makes it possible to detect a malfunction at an
early stage. The malfunction can also be in the clutch, and an
indication of this discrepancy is thus an early sign that the
vehicle should be serviced.
According to a particular aspect of the invention, it is possible
to make the device according to the invention self-teaching. This
means that the device, in a special operation without the aid of
the operator, will set the ratio between engine speed and vehicle
speed (or generator speed and vehicle speed) after the device has
been mounted in place. The micro-computer obtains the basic data to
make the calculations for the subsequent functioning of the device.
An advantage of this solution is that the device can be made in a
single version and need not be modified for different makes of
vehicles. It is even possible to mount it in any vehicle at all
without major modifications and without even ascertaining the
necessary data such as the gear ratios of the gear box and
transmission, tire dimensions etc.
Since a major purpose of the invention is to signal to the driver
when gear shifting is called for, it should also take into account
those situations where shifting is not called for despite the fact
that the engine speed is, under normal conditions, too high. For
example, a cold engine should not be made to pull hard at low
engine speed. It can therefore be advisable to add a function which
eliminates the signal for shifting up when the engine is cold. This
can be done either by connecting a thermoswitch to the engine or by
receiving a signal from the engine choke control.
According to a special embodiment, it is possible with the aid of
an accelerometer and the current speed signal to detect whether the
vehicle is travelling uphill or downhill and, in that case, prevent
the shift indication or raise or lower the set engine speed,
depending on the incline of the hill. It is also possible to take
the engine load into account, for example by an instantaneous value
of the fuel consumption (kg/h) to change the shift point.
Instead of setting the device so that when shifting to a higher
gear, a minimum speed will not be exceeded which is the same for
all gears, a certain fixed variation can be set in order to have
shifting to second gear end up at a lower engine speed than for
third and fourth gears. For example, the device can be set so that
shifting from first to second is done so that the engine speed in
second gear will be greater than 1400 rpm, from second to third
when the engine speed in third gear will be greater than 1450 rpm
and from third to fourth when the engine speed in fourth gear will
be greater than 1500 rpm.
Since the operating precondition is the fixed relationship between
engine speed and vehicle speed for each gear selection, it is
advisable to block the signal when the clutch pedal is depressed.
It is also advisable to arrange a sensor to sense when there is no
pressure on the accelerator, thereby locking the signal, so there
will be no signal for shifting during engine braking.
Another conceivable abnormal situation is if the driver has the
gear selector in the neutral position and has released the clutch
pedal while moving. If the apparatus is allowed to operate, the
result will obviously be erroneous, and if slippage sensing is
used, extreme slippage will be indicated, which is obviously
erroneous. A method of avoiding this is to arrange sensing of the
neutral gear selection position. Since this situation is so
abnormal, it should not require more attention than arranging a
filtering stop in the program, so that such a situation will not
result in a signal.
DESCRIPTION OF THE FIGURES
FIG. 1 shows a first embodiment, and
FIG. 2 shows a second embodiment of the invention. An embodiment of
the invention will now be described with reference to FIG. 1, which
shows a microprocessor arranged according to the principles of the
invention,
FIG. 3 is a flow chart illustrating the function carried out by the
circuit of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The microprocessor 1 which is a standard microprocessor (e.g.
Motorola 6805, see their handbook), has an input 2 coupled to a
speedometer or odometer. It is advisable to measure the speed of
one wheel of the vehicle which has a direct drive connection with
the gear box, e.g. the propeller shaft. It is possible to have the
speed signal come from a magnetic sensor which senses a permanent
magnet or the like fixed to a shaft, so that a pulse is sent every
time the shaft rotates.
A pulse signal from the car generator is coupled to the
microprocessor input 3. For an alternating current generator, the
current pulse is taken before rectification; for a direct current
generator, the changes in voltage during rotation can be used. In
both cases after appropriate pulse shaping, which will be obvious
to the person skilled in the art, a pulse series will be produced
with a pulse rate directly proportional to the rotational speed of
the generator and thus of the engine. It is also possible to sense
the actual rotational speed of the engine, for example with a
device with a magnet on the engine shaft and a stationary magnetic
sensor, or by using the ignition. Generator sensing is however
preferable due to the additional advantage of being able to detect
belt slippage.
The microprocessor now calculates a quotient between the two
speeds, which is an operation which is sufficiently wellknown to
the person skilled in the art to not require any explanation here.
The value obtained is compared with a series of gear values, one
for each gear in the vehicle gear box, so that the computer can
determine instantaneously which gear is engaged.
FIG. 3 demonstrates two purposes which are accomplished by the
present invention, the first of which, to be explained further, is
a detection of any slippage between the engine rotation speed and
vehicle speed caused by a malfunctioning clutch or other problem
which would result in changes in vehicle speed versus engine
rotational speed. The second portion of FIG. 3 demonstrates the
determination of the proper time to make a gear change.
Since one purpose of the invention is to see to it that a gear
change is recommended as soon as the engine speed after gear change
would exceed a certain minimum rpm, there is, for each gear
selection position, a maximum rpm stored in the memory, which
corresponds to the rpm at which shifting up would achieve this
minimum rpm after gear change. The current engine speed is compared
to said maximum rpm for the gear engaged, and if the actual engine
speed exceeds the maximum rpm, the LED 6 will be turned on.
In the preferred embodiment, the engine speed is multiplied by a
value corresponding to the quotient of the gear ratio for the next
highest gear divided by the gear ratio for the engaged gear. This
provides the engine speed which would have been obtained if the
next highest gear was selected. These steps are shown as the last
two steps on FIG. 3. FIG. 3 demonstrates, as will be described,
another purpose of the invention for determining when there is slip
between the engine and the drive train.
If the signal in one of the lines 4,5 is activated however, the LED
will not be turned on. These lines indicate a released accelerator
and a depressed clutch pedal respectively.
In accordance with an especially advantageous embodiment, the
device is self-teaching or adaptive and is carried out by the first
step shown in FIG. 3. This means that the quotients for the
different gear positions are set in a special setting operation
quite simply by engaging the various gears during a setting drive.
A manual setting means 7 can place the microprocessor in read mode
in which the quotients computed in the same manner as during
driving can be set, as shown in FIG. 3, including the first
decision block of FIG. 3 and the following flag setting step, gear
by gear.
According to another advantageous feature, there is a special
signal lamp 8 which will be permanently turned on if the quotient
measured during driving differs from the quotient read into the
memory. This means that the engine speed and the vehicle speed are
not in agreement, generally as a result of slippage, i.e. in the
clutch or of the generator belt. When the lamp 8 is lit, the driver
should have the situation diagnosed by a mechanic.
A more detailed improved embodiment will now be described with
reference to FIG. 2. In this case, a Motorola MC 6801
microprocessor is used. For more detailed information concerning
this microprocessor, see the "M6801, 8-Bit Single-Chip
Microcomputer, Reference Manual". The unit is coupled to a Volvo
Model 760 passenger car, which has a 4-cylinder 4-stroke engine. An
accelerator switch a, which closes when the accelerator is
depressed, and a clutch pedal switch, which also closes when the
pedal is depressed, in this case immediately prior to the actual
disengagement of the engine and the gear box. An engine speed
signal is received from the ignition system, preferably its primary
circuit, and produces a pulse for each cylinder ignition. There
will thus be two pulses per engine rotation.
One input d is connected to the 12 Volt ignition voltage, from the
wire conventionally called "15", and which is activated when the
engine is running.
A road distance signal from the speedometer system is fed into
input e. In the Volvo 760 there is a tooth wheel with 12 teeth in
the rear axle differential, and a sensor, which produces 12 pulses
for each rotation of the rear wheels of the vehicle. This pulse
train which is used for the speedometer is also used in this
example as a road distance signal.
It is obvious that the person skilled in the art, using the present
description, will be able to make quite a number of variations of
the inventive principle, and it is intended that all such
professional applications of the invention will be encompassed by
the patent claims.
* * * * *